Showing papers by "Varian Associates published in 1981"

Mode suppression means for gyrotron cavities

Abstract: In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

A Framework for Spectral Artifact Corrections in X-Ray CT

Abstract: The spectral artifact problem in X-ray computed tomography (CI) is well known. Many techniques have been suggested to correct for this problem, including linearization methods, iterative methods, and dual spectrum methods.

Cyclotron Resonance Devices

Abstract: Publisher Summary This chapter discusses the new class of microwave tubes that has emerged based upon the cyclotron resonance maser (CRM) instability. This class includes gyrotrons, gyroklystrons, and gyro traveling wave tubes. Their importance lies in their ability to produce more power at higher frequencies than other microwave tubes. In a gyrotron, gyroklystron, or gyro traveling wave tube (TWT) a beam of electrons having high transverse energy is formed in a magnetic field that produces a relativistic electron cyclotron frequency with a harmonic near the operating frequency of the tube. For every type of linear-beam microwave tube employing Langmuir wave or axial bunching, there is an analogous gyro device. In this chapter, the discussion is limited to those devices upon which there has been substantial work— that is, gyrotron oscillators, gyroklystron amplifiers, and gyro TWT amplifiers. The chapter discusses the theories common to all gyro devices and elaborates each kind of gyro device that reviews specific theoretical and experimental work. The theories discussed are Gyro device theory, Gyrotron Oscillator theory, Gyroklystron theory, and Gyro-TWT theory. No extensive review of the methods of forming electron beams for gyrotrons is included because the final design of these beams is usually determined by the empirical procedures that make extensive use of computer modeling. The chapter discusses the problems in all gyro devices— namely, mode competition, space charge, and velocity spread.

Grooved solar cell for deployment at set angle

Abstract: A grooved solar cell for deployment at a set angle with respect to incoming radiation has reduced contact obscuration and series resistance A regular array of walls formed by grooves in a crystalline semiconductor substrate is exposed to incoming radiation Metallic contacts are formed on those walls of the grooves which are not to be exposed to sunlight The solar cell is mounted in an apparatus at a set angle with respect to incoming radiation The array of walls is exposed to incoming radiation while the walls with metal contacts are substantially shadowed In a preferred embodiment the grooves are formed by using orientation specific etches

The growth and characterization of uniform Ga1-xInxAs (X ≤.25) by Organometallic VPE

Abstract: Compositionally uniform Ga1-xInxAs epitaxial layers with 0 ≤ x ≤ 0.2 5 have been grown by organometallic VPE on ◃100▹ GaAs substrates. Compositional uniformities of ±0.25 InAs percentage and ±5% thickness over a 3-cm long wafer have been achieved and are essentially independent of small changes in reactor geometry such as the angle of the susceptor tilt or wafer position on the susceptor. Growth has also been demonstrated at x = 0.52. The Ga1-xInxAs is grown using trimethylgallium (TMGa), triethylindium (TEIn) or trimethylindium (TMIn), and trimethylarsenic (TMAs). The use of TMAs eliminates the roomtemperature gas-phase reaction between AsH3 and either TEIn or TMIn, and allows one atmospnere pressure growth conditions to be used without any special mixing arrangements in the reactor. The comparative effects of using TEIn or TMIn as the In source are discussed in terms of crystal quality. Data on crystal composition as a function of gas phase composition and growth rate as a function of composition are presented, and n doping and carrier mobilities and p doping of Ga.80In.20As ars characterized. The vapor pressure of TMIn at 0°C is determined to be 0.21 mmHg.

Monolithic series-connected solar cell

Abstract: A monolithic series-connected solar cell comprises a series of cells (23, 24, etc.) each having a mesa-like structure which are electrically interconnected by a conductive lead (14) from the top of each cell to a contact ledge (20) formed in the base region of the adjoining cell. The individual cells are supported on an insulating substrate (15). The monolithic series-connected solar cell is fabricated from a fully formed single junction solar cell by forming a series of breaks down to an insulating substrate, forming a contact ledge in the base region on one side of the mesa defined by each break, applying a layer of insulating material (21) along the opposite side of each mesa and forming a conductive lead (14) between the top region of individual cells and the contact ledge of the adjoining cell.

NMR Probe coil system

Abstract: A saddle coil for operation in the probe of an NMR spectrometer is formed from coil portions of opposite helicities disposed on a flexible insulating material, the outer windings of said portions connected by a linking conductor disposed on said insulating medium, which medium is then deformed to form a cylindrical body.

Method and apparatus for on-column detection in liquid chromatography

Abstract: On-column detection by an optical detector is accomplished with a flexible silica column. The flexible fused silica column has an inner diameter less than 500 μm, an external protective coating with a stripped portion near the end of the column. The stripped portion is placed in the working path of an optical detector in order to detect and resolve the sample.

Stepped-gap achromatic bending magnet

Abstract: A first order achromatic magnetic deflection system for use in conjunction with a charged particle accelerator, is realized from a stepped gap manget wherein a charged particle propagated through the system is subject to at least two adjacent homogenous magnetic fields in traversing one-half of a symmetric trajectory through the system.

Improved mobility in OM-VPE-grown Ga1-xInxAs

Abstract: The use of a tirmethylindium-trimethylarsenic adduct, which is synthesised in the gas phase, as the In source, and AsH3 as the primary As source is reported for the growth of high-quality Ga1−xInxAs (x<0.20). The improved epitaxial layers have higher mobilities and lower background doping than those grown with trimethylarsenic as the sole As source. The effects of elevated growth temperatures are also reported.

Pattern data handling system for an electron beam exposure system

Abstract: A pattern data handling system for an electron beam exposure system wherein figure data conversion is performed simultaneously with irradiation of a workpiece, thereby providing high speed operation Figure data, containing figure descriptions for a stripe area, is subdivided into blocks of segment figure data and is stored in a pattern data memory Multiple pattern generators, each including a bit map memory, simultaneously convert blocks of segment figure data to bit maps and store the bit maps in their respective bit map memories The bit maps are transferred out of the bit map memories and through a shift register one at a time to provide continuous beam blanking data The system is particularly useful for electron beam exposure of reticles which are characterized by little or no repetition of features and by relatively large features

Particle beam accelerator

Abstract: An ion beam implanter includes a high energy accelerator having N electrodes equally spaced along the path of an ion beam, where N is an integer greater than 2. A resistor voltage divider has N terminals respectively connected to the N electrodes. Resistances of the divider between adjacent ones of the electrodes have the same value. A variable DC voltage source applies a high positive voltage to terminal N of the divider, while the first terminal of the divider is grounded. Terminal N is connected to an electrode that is upstream of the electrode connected to the first terminal. A shorting bar is dimensioned and positioned to selectively engage terminals N, (N-1 . . . 1. Drive means stepwise moves the shorting bar so an end portion of the bar sequentially engages terminals N, (N-1) . . . 1 in order. The remainder of the bar engages terminals N, (N-1) . . . (a+1) while the bar end portion engages terminal a, where a is selectively every integer from 1 to N. The stepwise movement of the shorting bar is synchronized with variations of the DC source to maintain a substantially constant voltage gradient along the length of the unshorted electrodes despite variations in energy applied to the beam by the accelerator. The drive means includes a pneumatically activated motor having rods with differences in length between fully extended and fully retracted positions thereof in binary relationship with the distance between adjacent ones of the N electrodes.

Single-pump multiple stroke proportioning for gradient elution liquid chromatography

Abstract: In a high-performance, high-pressure liquid chromatography system, gradient elution of solvent components from a plurality of component reservoirs can be accomplished according to a programmed temporally variable ratio by a single reciprocating pump. The pumping cycle comprises a plurality of fill strokes with intervening pumping strokes. During one of the fill strokes of the cycle, a proportioned mixture of solvent components is admitted to the pump chamber from the respective reservoirs by means of proportioning valves. During each of the other fill strokes of the cycle, only a single solvent component is admitted to the pump chamber. Consequently, a relatively low concentration of a particular component can be delivered by the pump with precision over a complete pumping cycle, although a comparatively higher and therefore more accurately measurable concentration of that component is admitted to the pump chamber during any given fill stroke. The opening and closing of the proportioning valves during the component proportioning fill stroke is sequenced to minimize deviations of the relative concentrations from the programmed concentration ratio. Proper sequencing of the proportioning valves reduces inaccuracies that would otherwise tend to occur, especially at the upper and lower concentration limits, due to effects related to the compressibility of residual solvent remaining in the pump chamber at the end of each pumping stroke.

Method for obtaining uniform etch by modulating bias on extension member around radio frequency etch table

Abstract: A method for etching a semiconductor wafer on an RF etch table employs a succession of different biases on an extension member positioned adjacent the periphery of the table. The extension member is electrically conductive, but is insulated from the etch table. The extension member is positioned with respect to the periphery of the table in a manner such that the plasma sheath induced above the etch table is continued beyond the periphery of the table, thereby eliminating the focusing of ions on the edges of an item being etched on the table. As different bias voltages are applied to the extension member, different etch profiles are experienced on the semiconductor wafer. The aggregation of etch profiles produces a more uniform overall etch.

Broadband high-power microwave window assembly

Abstract: Broadband High-Power Microwave Window Assembly A window assembly for a hollow waveguide of circular cross-section, with improved bandwidth and cooling capability for handling high microwave power transmissions over wide frequency ranges t is disclosed. A plate or disc of dielectric of refractive index n1 extends sealingly across the waveguide and has two parallel faces which exhibit a pattern of corrugations. One of these faces is in contact with a dielectric fluid of refractive index n2, and apparatus is provided for cooling and circulating the fluid over said one face. Each of the corrugations extends into the fluid a distance proportional to the inverse of the geometric mean of the product of the refractive indices n1, n2. In a preferred embodiment, a second plate is included, separated from the first by a region in which said dielectric fluid is circu-lated, and in which at least both the faces in con-tact with the fluid are corrugated. The corruga-tions not only result in greatly improved matching over a broad band, but also greatly improved fluid flow and surface contact thereof over said one face, for enhanced cooling and thus power handling capa-bility of the window assembly.

Magnetically enhanced sputter source

Abstract: A circular magnetron sputter source employs a central anode surrounded by an annular cathode of generally inverted conical configuration. The anode structure forms a composite anode and inner magnetic pole piece which is operated at or near ground potential. An outer magnetic pole piece concentrically surrounds the annular cathode. This outer pole piece is electrically isolated from the cathode, and held at or near ground potential. The cathode is operated at a potential of several hundred volts negative with respect to ground. The cathode is held in place by a novel retainer means and has a novel cross section configuration. Magnetic flux is provided either by permanent magnets or by electromagnets or by a combination of both located externally of the vacuum chamber in which the sputter source is operated. Magnetic field lines pass from the outer pole piece and through the cathode, exiting the sputter surface near the outer edge of the cathode. These magnetic field lines form an arch over the cathode by passing directly to the central anode without reentering the uneroded sputter surface of the cathode. In a circular geometry, these arching magnetic field lines form an endless tunnel for confining a glow discharge. The tunnel thus formed is a novel and modified magnetic tunnel in which electrons are reflected electrostatically from the cathode surface near the outer edge of the cathode and reflected by magnetic mirroring near the inner edge. Use of this modified magnetic tunnel leads to improved electrical impedance characteristics of the glow discharge and to improved uniformity in cathode erosion.

Molecular beam converters for vacuum coating systems

Abstract: This invention relates to coating of substrates in a vacuum system. A beam of molecules incident upon a molecular beam converter is transformed into a molecular beam flowing from the converter toward a substrate to be coated, or on which a layer is to be grown epitaxially. The incident beam is directed onto a heated impingement surface. In most embodiments the impingement surface generally faces the substrate to be coated, and the incident beam strikes the surface from the substrate side. A heating means maintains the impingement surface at a designated temperature. The heating means is separated and shielded from the impingement surface to avoid introducing contaminants from the heating means into the converted molecular beam, and also to avoid adverse physical and chemical effects on the heating means caused by the incident beam and its dissociation products. The incident beam may consist of gaseous compounds of normally solid materials which are at least partially dissociated at the heated impingement surface; the converted beam will then differ from the incident beam in direction, angular distribution, and molecular species. Alternatively, the incident beam may consist of atoms or molecules of elemental solids, in which case reflection and angular redistribution, with or without further dissociation, may occur at the heated impingement surface. Coating uniformity and step coverage can be improved by controlling the size and shape of the incident beam.

Sputter system incorporating an improved blocking shield for contouring the thickness of sputter coated layers

Abstract: The arbitrary contouring of thickness of a sputter-deposited film is made possible by a blocking means having a primary blocking shield and an ancillary blocking shield. The primary blocking shield intercepts atoms sputtered directly from the cathode target by line-of-sight transport. The ancillary blocking shield extends downwardly from the side of the primary blocking shield which is placed closest to the substrate. The ancillary blocking shield intercepts atoms sputtered from the cathode which by intervening gas collisions have been redirected to travel underneath the primary blocking shield. Precise tailoring of the thickness profile of the coating on the substrate is thereby provided and the quality of the composite film is maintained. The method for contouring the thickness of sputter coated layers comprises sputter coating portions of the film at successive stations. By employing the improved blocking shield at selected stations, the film in the aggregate may have the desired thickness contour.

Optoelectronic assembly including light transmissive single crystal semiconductor window

Abstract: An optoelectronic assembly obtains substantially improved coupling efficiency between small core optical fibers and small area detectors and emitters The assembly includes a housing containing an active optoelectronic device and a light transmissive single crystal semiconductor window The light transmissive single crystal semiconductor window seals the housing and physically protects the device from the environment The single crystal semiconductor window has an index of refraction higher than conventional glass windows, preferably greater than 2, in order to reduce beam spreading between the optical fiber and small area detectors or emitters The window material is preferably single crystal GaP

Performance characteristics and extended lifetime data for InGaAsP/InP LED's

Abstract: The performance and lifetest results of InGaAsP/InP LED's emitting at 1.27 µm are described. At a current density of 10 kA/cm2, 40 µW of optical power is coupled into a 63 µm core, 0.21 NA optical fiber, and the projected lifetime at room temperature is approximately estimated to be 8 × 1010hours.

A gyro-TWT with a space-charged limited gun

Abstract: Most gyrotron traveling wave tubes (gyro-TWT) currently employ temperature-limited magnetron-injection electron guns to produce electron beams with high perpendicular to parallel velocity ratios. Certain problems with these guns have inspired the investigation of alternative space-charge-limited guns. An improved design technique applied to the helical transverse, magnetic "wiggler" employed in early cyclotron maser experiments shows promise for high power operation. A previously reported C-band gyro-TWT has been modified. The magnetron injection gun has been replaced with a Pierce-type electron gun. A bifilar helix of prescribed length capable of producing a helically varying transverse magnetic field for converting axial electron energy into transverse electron energy of low energy spread was placed between the Pierce gun and the rf interaction circuit. The rf interaction circuit was not changed. Substantial output power was achieved. Comparison of initial experimental results with previous results using the magnetron injection gun are presented.

Fluorescent composition, a process for synthesizing the fluorescent composition

Abstract: A fluorescent composition useful in thin-layer chromatography comprises an inert porous particle having a fluorescent material fixedly attached by covalent chemical bonding to the surface thereof. A process for synthesizing this fluorescent composition is disclosed. A method for detecting the radioactivity of a radioactive species using a cell packed with such a fluorescent composition is also disclosed.

Improved measurement of neutron spectrum from 35 MeV protons on thick beryllium.

Abstract: The energy spectrum of neutrons produced by 35 MeV protons on 1.6 cm thick beryllium has been measured at O /sup 0/ by means of proton recoil spectroscopy. We find substantial agreement with other measurements.